I would generally agree with what gewecke says. Either the Pro 197 or the Pro 106, depending on what your needs are probably, is the cheapest 'digital' type of scanner on the market currently. I won't get into the pros or cons of the scanner brands here otherwise I'll go off topic. The only thing that these two scanners don't support is LTR. Correct if I'm wrong, but its my understanding that using on LTR on public safety systems is on the decline.
The Pro-197 & Pro-106 each will do LTR, which is used used by a few smaller departments in my area (though that's certainly not the case everywhere).
It is the previous model digital scanners sold by Radio Shack, the Pro-96 (handheld) & Pro-2096 (base/mobile) that do not trunk track LTR. They also do not receive mil-air or 700mhz frequencies out of the box. While those frequencies can be "unlocked" by software such as Win96, the performance may be unpredictable. Also, even though 700mhz can be received if unlocked, the 96/2096 scanner series still would not trunk track a system using those frequencies.
The Pro-106/-197 (GRE equivalents PSR-500/PSR-600) will do LTR, mil-air, 700mhz trunking, etc. As will the current Uniden digitals, BCD396XT (handheld) or BCD996XT (base/mobile). So will the previous versions, BCD396T & BCD996T. With the exception of the BCD396T & BCD996T, the rest of this group will can also utilize the
NAC code used on conventional P25 (digital, but not on a trunked system). That's an advantage that the older digitals (Pro96, BC296D, BC250D) don't have either.
In general, the digital scanners have more memory capacity for frequencies and talkgroups, as well as a few additional features, than their analog stablemates from the same manufacturer. See the
Wiki for more comparison information.